Re: Helix Match

Hi Richard , Gang
I have searched the contents of " Antennas by John Kraus 2nd edition "
for anything on a monofilar helix with separate reflectors. I have not
found anything, even in large arrays ( 96 helix ) . There are many
various arrays but all have a common reflector ( launcher ).
The four helix array that folks are referring to here on the BB was
originated in 1948 by J. D Kraus " Helical Beam Antennas For wide-Band
Applications." Proc. IRE, 36, 1236-1242, october 1948 .
This array is shown in the above 2nd edition with the beamwidth, axial
ratio and VSWR graphs as a function of frequency . It uses a single
reflector 2.5 lambda on a side. With the centers of the helices at 1.5
lambda spacing. The helices had a diameter of .3 lambda , 14 degree
and six turn . The frequency band width was greater than 300 mHz .
The tapered matching lines were used to transform the 140 ohm impedance
of each helix to 200 ohms so that four helices in parallel would match a
53 ohm line. The tapered lines are one lambda long. The lowest
frequency had a gain of 18 db an the high end had a gain of 21 db
The axial ratio of the four was very reasonable ( 1.1:1 or so across the
band width ) . Beam width became narrower ( couple of degrees ) as
the frequency increased. VSWR was also acceptable ( < 2:1) across
the band.
In conclusion I suppose I am still at the same place since your antenna
has separate reflectors.
I do thank you for responding to my query.
73's Joe Murray K0VTY
________________________________________________________________
YOU'RE PAYING TOO MUCH FOR THE INTERNET!
Juno now offers FREE Internet Access!
Try it today - there's no risk! For your FREE software, visit:
http://dl.www.juno.com/get/tagj.
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org